The population of older adults is steadily growing, and there is an urgent need to understand the basis of older adults' impairment in the ability to link together multiple pieces of information (associative memory), which is critical for everyday memory function. Aging theory has suggested that older adults suffer from a global decline in the ability to form associative memories while theories of associative memory based on young adult data suggest that associative memory itself is supported by multiple cognitive processes. These two theories have not been integrated and tested together in an aging population. The long-term goal of this research is to gain a substantial understanding of associative memory mechanisms in older adults so that therapeutic intervention strategies for memory can be developed. The objective of this application is to integrate two theories of associative memory in order to better understand the mechanisms of age-related changes in associative memory function. The overarching hypothesis is that young and older adults rely on similar functional organization among MTL subregions, but that hippocampal decline in older adults results in a shift toward greater contributions by MTL cortical areas in successful formation of associations. This hypothesis is formulated based on studies in young adults that have found that the hippocampus is broadly involved in the formation of associations, whereas the perirhinal and parahippocampal cortices are selectively involved in particular types of associations. Importantly, the involvement of perirhinal cortex in associative encoding also depends on the extent to which a task encourages unitization, which suggests that the degree of engagement of MTL structures can be modulated through the use of encoding strategies. The rationale for the proposed research is that, by extending the current work regarding associative memory in young adults to aging, we will have a clearer idea of how subregions of the MTL support associative encoding across the lifespan. Novel fMRI studies are proposed to: 1) Test the neural basis of the Associative Deficit Hypothesis and expand the Binding of Item and Context Model to aging and 2) Investigate the role of unitization in successful encoding of both item-item and item- context associations in healthy older adults. The approach is innovative because it directly tests the neural mechanisms underlying two prominent theories of associative memory in older adults, as well as examining means by which to ameliorate age-related deficits in associative memory. A novel paradigm will be used that combines manipulations of both association type and encoding strategy to elucidate the neural substrates of associative memory within the MTL of older adults. The proposed research is significant because it is the first critical step toward unified explanation of how age differences in associative memory are related to the functional organization of the MTL. This research has the potential to lead to improvements in older adult memory function and quality of life through the development of intervention strategies for memory and by helping to dissociate normal aging from early signs of dementia.